Re: [Qemu-devel] [RISU RFC PATCH v1 2/7] risugen_x86_asm: add module

[Richard Henderson]

On 6/19/19 7:04 AM, Jan Bobek wrote:
> +sub rex_encode(%)
> +{
> +    my (%args) = @_;
> +
> +    $args{w} = 0 unless defined $args{w};
> +    $args{r} = 0 unless defined $args{w};
> +    $args{x} = 0 unless defined $args{w};
> +    $args{b} = 0 unless defined $args{w};

What makes you believe that REX.[RXB] are dependent on REX.W?
Or are these merely cut-and-paste errors?


> +sub modrm_encode(%)
> +{
> +    my (%args) = @_;
> +
> +    die "MOD field out-of-range: $args{mod}"
> +        unless 0 <= $args{mod} && $args{mod} <= 3;
> +    die "REG field out-of-range: $args{reg}"
> +        unless 0 <= $args{reg} && $args{reg} <= 7;
> +    die "RM field out-of-range: $args{rm}"
> +        unless 0 <= $args{rm} && $args{rm} <= 7;
> +
> +    return (value =>
> +            ($args{mod} << 6)
> +            | ($args{reg} << 3)
> +            | $args{rm},
> +            len => 1);
> +}
> +
> +sub sib_encode(%)
> +{
> +    my (%args) = @_;
> +
> +    die "SS field out-of-range: $args{ss}"
> +        unless 0 <= $args{ss} && $args{ss} <= 3;
> +    die "INDEX field out-of-range: $args{index}"
> +        unless 0 <= $args{index} && $args{index} <= 7;
> +    die "BASE field out-of-range: $args{base}"
> +        unless 0 <= $args{base} && $args{base} <= 7;
> +
> +    return (value =>
> +            ($args{ss} << 6)
> +            | ($args{index} << 3)
> +            | $args{base},
> +            len => 1);
> +}

These are interdependent, in that SIB requires MODRM.RM == 4.  But I don't see
anything that either enforces that or validates it, either here or within
write_insn below.


r~